Femtocell technology is a hot issue in the telecommunication industry. It is a solution for extending mobile telecommunication indoor coverage, and can transmit voice or data call initiated by a mobile user terminal, for example mobile phone or Personal Digital Assistant (PDA), to the 3G mobile Core network based on the standard interface via the backhaul in the fixed network. That is, Femtocell technology takes the fixed network as its backhaul and its family access point is plug and play, and can be connected to any IP based transmitting network.
The wireless propagation feature of traditional macro cell is bad penetration performance against buildings, which cause the indoor service quality to degrade. The emerging of the Femtocell technology effectively improves the indoor coverage and service quality.
FIG. 1 shows a schematic diagram of transmitting mobile Multimedia Broadcast/Multicast Service (MBMS) via fixed backhaul in the existing telecommunication network using Femtocell technology. As shown in FIG. 1, the telecommunication network comprises the mobile base station 1, for example, the Base Station Router (BSR) (also called eNodeB or home NodeB) 1, the Access Node(AN) 2, the edge router 3, the Femtocell Gateway(GW) 4 and the Broadcast Multicast Service Center (BM-SC) 5. The Femtocell Gateway 4 is configured between the mobile core network and public IP network, and the Femtocell Gateway 4 converges and provides standard interfaces oriented to the mobile core network, for example, Iu_CS, Iu_PS, Gn/Gi and other network side interfaces. The BSR 1 is connected to the fixed access network via the access node 2. The fixed access network may be ADSL network, or FTTX network. FIG. 1 shows four BSRs 1a, 1b, 1c and 1d and two access nodes 2a and 2b n. Wherein, the BSRs 1a and 1b are connected to the access node 2a, and the BSRs 1c and 1d are connected to the access node 2b. The access nodes 2a and 2b establish connection with the edge router 3 via fixed access network or convergence network, and the edge router 3 is accessed to the public IP network, and is eventually connected to the mobile core network via the Femtocell GW 4. Wherein, the BM-SC 5 in the mobile core network provides mobile broadcast and multicast service. It can be appreciated that the four BSRs and two access nodes shown in FIG. 1 are only illustrative, the practical network is not limited to the above configuration or the number of network elements in the above configuration.
The process of wireless data transmission in the prior art is described briefly in the followings. When the mobile user terminal, such as a mobile phone or a PDA request the multicast service from the mobile core network, the mobile user terminal equipment sends multicast join message, for requesting to join in the multicast group. Accordingly, the BSR will send the multicast join message via Internet Protocol Security Tunnel (IPSec Tunnel). That is, encapsulating the multicast join message in the IPSec packet, and the destination address of the encapsulated IPSec packet is the egress of the tunnel, i.e., the Femtocell GW 4, and the source address of the encapsulated IPSec packet is the ingress of the tunnel, i.e., the IP address of the BSR. Similarly, when the mobile user terminals dominated by the BSR 1b-1d all request for the multicast service, the three BSRs respectively send the multicast join message via different IPSec tunnels. Under this situation, the multicast join message is directly sent via unicast tunnel from the corresponding BSR to the Femtocell GW 4, and the tunnel passes the fixed access network, and therefore, the multicast join message is invisible to each network element in the fixed access network, for example, access node, switch, router or edge router, thus the multicast backhaul can not be established in the fixed network, and therefore, the multicast service data can only be transmitted in unicast form in the fixed network. Therefore, when the mobile user terminal equipments dominated by the BSR 1a-1d all request multicast service from the BM-SC 5, even if the four BSRs request the same multicast service from the mobile core network, for example, multicast service 60, the Femtocell GW 4 still sends four copies of the multicast service 60, that is 60a,60b, 60c and 60d to the four BSRs via four IPSec tunnels in unicast form, that is sending to BSRs 1a-1d in unicast form.
Therefore, the existing method of transmitting MBMS services between the mobile core network and the Femtocell occupies huge network resources in the fixed network, and brings a heavy working burden to the network devices, such as gateway, edge router, and access node.